[PATCH] getdelays: Fix netlink attribute length

From: David Ahern
Date: Fri Mar 27 2020 - 13:31:24 EST


A recent change to the netlink code:
6e237d099fac ("netlink: Relax attr validation for fixed length types")
logs a warning when programs send messages with invalid attributes
(e.g., wrong length for a u32). Yafang reported this error message
for tools/accounting/getdelays.c.

send_cmd() is wrongly adding 1 to the attribute length. As noted in
include/uapi/linux/netlink.h nla_len should be NLA_HDRLEN + payload
length, so drop the +1.

Fixes: 9e06d3f9f6b1 ("per task delay accounting taskstats interface: documentation fix")
Signed-off-by: David Ahern <dsahern@xxxxxxxxxx>
Tested-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Cc: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Cc: Shailabh Nagar <nagar@xxxxxxxxxxxxxx>
---
tools/accounting/getdelays.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/accounting/getdelays.c b/tools/accounting/getdelays.c
index 8cb504d30384..5ef1c15e88ad 100644
--- a/tools/accounting/getdelays.c
+++ b/tools/accounting/getdelays.c
@@ -136,7 +136,7 @@ static int send_cmd(int sd, __u16 nlmsg_type, __u32 nlmsg_pid,
msg.g.version = 0x1;
na = (struct nlattr *) GENLMSG_DATA(&msg);
na->nla_type = nla_type;
- na->nla_len = nla_len + 1 + NLA_HDRLEN;
+ na->nla_len = nla_len + NLA_HDRLEN;
memcpy(NLA_DATA(na), nla_data, nla_len);
msg.n.nlmsg_len += NLMSG_ALIGN(na->nla_len);

--
2.17.1